Sylius is an Open Source eCommerce Framework on Symfony. CurrencySwitchController::switchAction(), ImpersonateUserController::impersonateAction() and StorageBasedLocaleSwitcher::handle() use the HTTP Referer header directly when redirecting. The attack requires the victim to click a legitimate application link placed on an attacker-controlled page. The browser automatically sends the attacker's site as the Referer, and the application redirects back to it. This can be used for phishing or credential theft, as the redirect originates from a trusted domain. The severity varies by endpoint.

public endpoints require no authentication and are trivially exploitable, while admin-only endpoints require an authenticated session but remain vulnerable if an admin follows a link from an external source such as email or chat. The issue is fixed in versions: 1.9.12, 1.10.16, 1.11.17, 1.12.23, 1.13.15, 1.14.18, 2.0.16, 2.1.12, 2.2.3 and above.